Over the past several years, the performance of microelectronic devices fabricated on semiconductor substrates has rapidly improved. Processing speeds have increased dramatically as device technology nodes have shrunk. For the most part, the dramatic improvements in microelectronic device performance have resulted from the use of the same underlying manufacturing technology. For instance, manufacturing of a microprocessor device on a silicon substrate involves patterning several layers of features in the silicon and depositing metal, such as aluminum or copper, in the features. These different layers of features are created by shining radiant energy on multiple photomasks, also known as masks or reticles.
A photomask typically includes a patterned layer formed on a substrate. The photomask is typically formed by writing data from a mask pattern file into a resist layer of a photomask blank, developing portions of the resist layer, and etching exposed areas of an opaque layer (e.g., chrome) to form the patterned layer. Before the mask pattern file is written on the photomask blank, a rule checking system may evaluate the mask pattern file to determine the smallest feature size in the mask pattern file before a defect is detected.
Depending on the type and complexity of a set of design rules associated with a manufacturing process, the rule checking process may not accurately detect a potential violation in the mask pattern file, especially in light of the expanding number of features found on photomasks. Photomask manufacturers have attempted to reduce the number of false detections by incorporating design rules with the rule checking system. By combining the design rules with the rule checking system, a process is created for analyzing and evaluating the data in the mask pattern file in order assess whether a photomask may be fabricated with a selected manufacturing process.
Conventional design rules typically focus on a minimum width for a linear feature, such as an interconnect between at least two features, on the photomask. When these simple design rules are applied to more complex features (e.g., serifs), false defects may be detected in the mask pattern file during a rule checking process because the conventional design rules may require that the diagonal of the feature be greater than or equal to the minimum line width. Each one of the detected defects are then analyzed by a technician to determine if the flagged feature is a false defect or a rule violation indicating that the feature cannot be formed on the photomask with the selected manufacturing process. This type of manual analysis increases the time and effort needed to manufacture a photomask and may be prone to errors.